We propose a three year study to investigate the epidemiology of malignant tumors of the skin and mucous membranes of the anogenital area. Specifically we will focus on epithelial carcinomas of the anus, vulva, and penis. The study is designed to test for multiple antecedent risk factors for these tumors, with special emphasis on sexually transmitted disease and chronic irritation primarily in the form of sexual practices and anogenital conditions and treatments. We plan to use the case-control method. The case group will consist of 400 persons: 100 men and 100 women with squamous or transitional cell carcinomas of the anus or perianal skin, 100 women with squamous cell carcinoma of the vulva, and 100 men with squamous cell carcinoma of the penis. All cases will be identified by the Los Angeles County/USC Cancer Surveillance Program. Controls will be neighborhood controls matched to the cases by date of birth ((plus/minus) 5 years), sex, and race. Data will be obtained by personal interviews (in respondent's homes) by trained interviewers using a structured questionnaire, focusing on the above variables. A 25cc blood specimen will also be collected by the interviewer. Antecedent anogenital conditions which have been medically diagnosed and treated will be verified using hospital and clinical records on the first 25 case-control pairs within each sex-site category, and on all respondents if the verification process proves to provide additional information. In the analysis we will evaluate both the relative importance of each suspected risk factor within each site and sex, and the consistency of findings across sites and sexes.